Double-offset Pneumatic Butterfly Valve (Wafer Type) | Metal Seated | Fire-Safe Certified

Double eccentric (double offset) valves add a third geometric offset - the sealing cone is angled relative to the pipe centerline. This creates a cam-action where the disc lifts away from the seat before rotating, eliminating all rubbing contact. Double eccentric valves only have two offsets and still experience some seat contact during rotation. Double eccentric valves provide metal-to-metal sealing, higher temperature capability (-29°C to +400°C), and zero leakage (Class VI), while double eccentric valves typically use soft seats and are limited to approximately -40°C to +200°C.

The double offset geometry creates a torque-seated mechanism rather than position-seated. When closing, the angled disc edge (third offset) cam-actions into the matching angled seat, creating uniform circumferential contact pressure. This metal-to-metal interference fit eliminates the need for soft elastomers that degrade over time. The seating force is generated by operating torque, ensuring consistent sealing pressure even as thermal cycles cause expansion/contraction of metal components.

Double eccentric valves require minimal maintenance due to their frictionless design. Recommended practices include: (1) Periodic stem packing adjustment if leakage is observed - graphite packing can be tightened while valve is in service; (2) Actuator maintenance check every 12 months using lithium-based grease; (3) Seat inspection every 3-5 years depending on service severity; (4) In-line seat replacement is possible without removing valve from pipeline, reducing downtime. Unlike soft-seated valves, metal seats do not require periodic replacement under normal conditions.

Yes, our double eccentric valves are specifically designed for cryogenic service down to -196°C (-320°F). Critical features for LNG applications include: extended bonnet to keep stem packing away from cold media, deep cryogenic materials (CF8M body, Inconel 718 stem), graphite packing rated for thermal cycling, and bonnet drip lip to prevent ice formation on stem. All valves for cryogenic service receive special cleaning and degreasing to remove hydrocarbons, then are tested with liquid nitrogen to verify sealing at operating temperature.

Standard delivery is 4-6 weeks for sizes DN50-DN600 from our Shanghai manufacturing facility. Larger sizes DN700+ may require 8-12 weeks depending on material specifications. Expedited production available for critical projects. All XHVAL valves carry a 24-month warranty from date of installation or 30 months from shipment, whichever occurs first. Warranty covers manufacturing defects, material flaws, and performance to published specifications. XHVAL maintains replacement parts inventory for 20+ years to support long-term operation.